Flood Simulation in Gin-River Basin of Sri Lanka Using One-And Two-Dimensional Hydrodynamic Models

Prabhath Ransara, Amila Silva, Aparna Rangana

Wednesday 1 july 2015

12:39 - 12:42h at South America (level 0)

Themes: (T) Flood risk management and adaptation, (ST) Flood risk assessment, Poster pitches

Parallel session: Poster pitches: 9J. FloodRisk - Assessment

Flood modeling and mapping have become most essential component in the sense of flood risk management. Historical data in recent decades show that upward trend in occurrence of natural disasters across the globe. Sri Lanka is an island in the Indian Ocean which is having 103 distinct river basins those enriching agriculture and livelihood. However, water related disasters are quite frequent due to the rainfall pattern. Most of the basins are subjected to devastations frequently as cruel weather conditions. Gin river basin, the study area of this research is located entirely in the wet zone, as a result number of downpours receive throughout the year. Gin river basin boasts many geographic features such as mountains and flat terrains. Central part of the basin is flooded regularly while a massive flood hit the area in 2003, raising water level by 5 meters while 800 houses going under water. Therefore, need of a flood risk assessment and setting up an early warning system for the basin became important and highlighted by many researchers recently. This paper presents an attempt to fill that research gap. The research findings would be advantageous for all stake holders in the basin including decision makers. The study consist setting up a comprehensive hydro dynamic model including rainfall runoff modeling and flood mapping. Delft-Sobek is chosen as the modeling tool and ArcGIS is used for mapping. Furthermore, cross sections extracted from a bathymetric survey and Digital Elevation Model (DEM) of 20m resolution is used as major inputs for the model. The usefulness of the study is demonstrated in a case study scenario for extreme hydrological events. Key works: Flood Risk Assessment, Flood Modeling, Delft-Sobek